This invention relates to a process for detecting and tracking a welded joint in a length of material to be processed in a continuous production line, i.e., a so-called tracking process, for a continuous steel material such as in a continuous steel pipe production line, continuous hot dipping line, continuous annealing line, continuous pickling line and the like.
It has hitherto been proposed that in a steel pipe production plant, such as a forged steel pipe line, steel strips in the form of a coil should be welded together end to end for feeding same through a continuous production line.
The welded joints thus produced are unique in their mechanical strength and in their appearance, as compared with the rest of the steel strips.
In addition, there tends to take place a variation in the thickness between the steel strips upstream and downstream of a welded joint due to the limited accuracy of thickness control in the preceding processing of the steel strip, i.e., in the rolling thereof.
Although the technique of welding at the present time is highly developed, it is preferred that welded joints not be included in a product which is being delivered from the output of a production line, for reasons of both mechanical strength and appearance. Nevertheless, the welded joints are of importance in the automatic control of a production line.
Hitherto, manual means have been resorted to for recognition or detection of welded joints moving along a production line. In addition, even in the case of an automatic production line, suitable markings have been put on welded joints of a continuous length of material for subsequent detection by a detecting means located in a suitable position for tracking and detecting the movements of welded joints. As a marking method, a hole may be drilled in the neighborhood of a welded joint in a material, or a paint or magnetic substance may be applied thereto. However, drilling the material imparts a serious defect to the quality of the final product and may pose many problems in working and strength, while a paint or a magnetic substance may not be used for a production line including heat treatment.
The visual recognition or detection of a welded joint by an operator may lead to error, particularly in view of the improved appearance of welded joints owing to progress in welding technology, and requires an expenditure of man power, with accompanying reduced efficiency and poor accuracy of recognition.
It is a principal object of the present invention to provide a process for tracking a welded joint in a continuous length of a material passing through a continuous production line by detecting a welded joint accurately automatically.
It is a further object of the present invention to clarify the relationship between the results of tracking and respective equipments provided in a production line.
It is a still further object of the present invention to provide a method for correcting an error of the results of tracking.
It is a further object of the present invention to provide a method for setting a gate for use in the aforesaid error correcting method.
It is a further object of the present invention to provide a presumption method for an anticipated length of material extending from one welded joint to the next welded point.
It is a further object of the present invention to provide a detecting method for a welded joint.
It is a further object of the present invention to provide an assembly of a detector for a welded joint.
It is a further object of the present invention to provide a continuous production line to which the tracking process of the present invention is applied.
It is a further object of the present invention to provide processing of tracking information.
It is a further object of the present invention to provide a method for setting a presettable counter.
It is a further object of the present invention to provide a method for utilizing the results of tracking.